1. Field of the Invention
This invention relates to a semiconductor memory device with a plurality of one transistor memory cells and a sense amplifier circuit comprised of a flip-flop circuit having a plurality of MIS transistors, and moreover relates to an improvement in the driving circuit for the sense amplifier circuit of this type.
2. Description of the Prior Art
A memory device of which memory cells are respectively composed of one MOS FET and one memory capacitor is generally capable of discriminating "1" or "0" values of the stored data in accordance with the fact that an output voltage of this capacitor is higher or lower than the specified threshold level. However, because of small difference of output voltage of the cell and the threshold voltage, the output voltage is generally amplified by the sense amplifier which forms a flip-flop circuit. In such a sense amplifier circuit, the difference between the output voltage of the cell in the memory device and the threshold voltage is small and therefore such amplifier circuit causes a following disadvantage that when the stored data is, for example, "1", the cell output which should originally be higher than the threshold voltage becomes lower than it due to deviation of the resistance of wirings in the flip-flop circuit, thereby causing an error data. Thus, as a means for solving this disadvantage, the technique of gradually increasing a current which flows through the flip-flop circuit is proposed by Clinton Kuo et al. of Texas Instruments, Dallas, Tex. in Electronics, May 13, 1976. Particularly, description of the second column in the left side on page 83 is closely related to such content and the left upper figure on page 84 may be referred as the reference. According to this technique, a multiple grounding path having three transistors is provided for the flip-flop circuit, whereby these three transistors are made conductive by means of different three clocks and resultingly a current flowing through the flip-flop circuit is gradually increased. However, such technique requires three different clocks and therefore requires a means for generating such clocks, making the circuit configuration complicated.